Keywords: 
• Dendrobium nobile Lindl /
• mycorrhizal fungi /
• endophytic bacteria /
• symbionts

Abstract: An attempt was made to investigate the naturally occurring, difficult-to-separate combinations of mycorrhizal fungi and endophytic bacteria found in the mycorrhizae of Dendrobium nobile Lindl. Three groups of artificially cultivable and separable natural combinations of mycorrhizal fungi and endophytic bacteria were isolated,screened, and identified. Through co-cultivation experiments and functional assessments, the symbiotic relationships and mechanisms among these combinations were analyzed. The results showed that G2 and G8 are symbiotic combinations of Bacillus and Fusarium solani, while G17 is a combination of Bacillus and Diaporthe phaseolorum.There is an antagonistic relationship between the G2 and G17 combinations, leading to an increased total growth,whereas the G8 combination exhibits no antagonistic relationship, with mutual promotion between the two. The fungi in the G2 and G17 combinations possess strong cellulolytic abilities, with clear zone diameters of 27.62 mm and 21.52 mm,respectively, while the bacteria exhibit nitrogen-fixing abilities of 1.69 μg·mL^-1 and 1.68 μg·mL^-1, respectively. The strong cellulolytic and nitrogen-fixing abilities contribute to the antagonistic relationship between the G2 and G17combinations. In the G8 combination, the fungal solution contains the lowest hydrolyzed phosphorus, while the bacteria have the highest phosphorus-solubilizing ability, reaching 39.07 mg·kg^-1, indicating a complementary functional relationship. Therefore, natural symbiotic combinations exhibit various forms of symbiotic relationships, including complementarity, promotion, and inhibition, and there is a correlation between function and symbiotic relationship.